For many years it has been common practice to use a movable magnetic core within the actuating electromagnetic coil of a circuit breaker. Commonly the movable core has been a cylindrical structure supported and guided in a non-magnetic tube spring and/or gravity urged away from the pole piece, and rather commonly immersed in a damping fluid to delay the movement of the core toward the pole piece. When the breaker contacts are closed, the current flows through the coil and begins to urge the core toward the pole piece. However, only when the current reaches predetermined overload level is the force strong enough to urge the core to the pole piece and, in turn, attract the movable armature of the breaker toward the pole piece, thereby tripping the breaker and releasing the contacts.
In the past, in order to positively hold the tube supporting the core in position it has been necessary to employ means mechanically connecting the tube to the coil and the frame, thus necessitating fabrication of a sub-assembly which is different for each type of coil and for each combination of other components which comprise the various sub-assemblies. Then it is necessary to maintain a sub-assembly inventory of many types of sub-assemblies ready for use in various types of breakers. Maintaining such an inventory is costly and separately assembling the sub-assemblies and the final breaker assembly is inefficient. At the present time, any changes to parts requires costly off the line salvage disassembly with losses of valuable parts.